read struct refs as array

2025-12-25 16:09:30 +01:00 · 2019-04-10 18:52:22 +02:00
parent 52ec698635
commit 654510f3ff
8 changed files with 161 additions and 177 deletions
--- a/src/utils/structEncoding.js
+++ b/src/utils/structEncoding.js
@@ -23,9 +23,7 @@ import {

 import * as encoding from 'lib0/encoding.js'
 import * as decoding from 'lib0/decoding.js'
-import * as map from 'lib0/map.js'
 import * as binary from 'lib0/binary.js'
-import * as iterator from 'lib0/iterator.js'

 /**
 * @typedef {Map<number, number>} StateMap
@@ -43,48 +41,53 @@ export const structRefs = [
 ]

 /**
- * @param {decoding.Decoder} decoder
- * @param {number} structsLen
- * @param {ID} nextID
- * @param {number} localState next expected clock by nextID.client
- * @return {IterableIterator<AbstractRef>}
+ * @param {encoding.Encoder} encoder
+ * @param {Array<AbstractStruct>} structs All structs by `client`
+ * @param {number} client
+ * @param {number} clock write structs starting with `ID(client,clock)`
 */
-const createStructReaderIterator = (decoder, structsLen, nextID, localState) => iterator.createIterator(() => {
-  let done = false
-  let value
-  do {
-    if (structsLen === 0) {
-      done = true
-      value = undefined
-      break
-    }
-    const info = decoding.readUint8(decoder)
-    value = new structRefs[binary.BITS5 & info](decoder, nextID, info)
-    nextID = createID(nextID.client, nextID.clock + value.length)
-    structsLen--
-  } while (nextID.clock <= localState) // read until we find something new (check nextID.clock instead because it equals `clock+len`)
-  return { done, value }
-})
+const writeStructs = (encoder, structs, client, clock) => {
+  // write first id
+  const startNewStructs = findIndexSS(structs, clock)
+  // write # encoded structs
+  encoding.writeVarUint(encoder, structs.length - startNewStructs)
+  writeID(encoder, createID(client, clock))
+  const firstStruct = structs[startNewStructs]
+  // write first struct with an offset
+  firstStruct.write(encoder, clock - firstStruct.id.clock, 0)
+  for (let i = startNewStructs + 1; i < structs.length; i++) {
+    structs[i].write(encoder, 0, 0)
+  }
+}

 /**
- * @param {encoding.Encoder} encoder
- * @param {Transaction} transaction
+ * @param {decoding.Decoder} decoder
+ * @param {number} numOfStructs
+ * @param {ID} nextID
+ * @return {Array<AbstractRef>}
 */
-export const writeStructsFromTransaction = (encoder, transaction) => writeStructs(encoder, transaction.y.store, transaction.beforeState)
+const readStructRefs = (decoder, numOfStructs, nextID) => {
+  /**
+   * @type {Array<AbstractRef>}
+   */
+  const refs = []
+  for (let i = 0; i < numOfStructs; i++) {
+    const info = decoding.readUint8(decoder)
+    const ref = new structRefs[binary.BITS5 & info](decoder, nextID, info)
+    nextID = createID(nextID.client, nextID.clock + ref.length)
+    refs.push(ref)
+  }
+  return refs
+}

 /**
 * @param {encoding.Encoder} encoder
 * @param {StructStore} store
 * @param {StateMap} _sm
 */
-export const writeStructs = (encoder, store, _sm) => {
+export const writeClientsStructs = (encoder, store, _sm) => {
  // we filter all valid _sm entries into sm
  const sm = new Map()
-  const encoderUserPosMap = map.create()
-  const startMessagePos = encoding.length(encoder)
-  // write diff to pos of end of this message
-  // we use it in readStructs to jump ahead to the end of the message
-  encoding.writeUint32(encoder, 0)
  _sm.forEach((clock, client) => {
    // only write if new structs are available
    if (getState(store, client) > clock) {
@@ -99,59 +102,28 @@ export const writeStructs = (encoder, store, _sm) => {
  // write # states that were updated
  encoding.writeVarUint(encoder, sm.size)
  sm.forEach((clock, client) => {
-    // write first id
-    writeID(encoder, createID(client, clock))
-    encoderUserPosMap.set(client, encoding.length(encoder))
-    // write diff to pos where structs are written
-    encoding.writeUint32(encoder, 0)
-  })
-  sm.forEach((clock, client) => {
-    const decPos = encoderUserPosMap.get(client)
-    // fill out diff to pos where structs are written
-    encoding.setUint32(encoder, decPos, encoding.length(encoder) - decPos)
-    /**
-     * @type {Array<AbstractStruct>}
-     */
    // @ts-ignore
-    const structs = store.clients.get(client)
-    const startNewStructs = findIndexSS(structs, clock)
-    // write # encoded structs
-    encoding.writeVarUint(encoder, structs.length - startNewStructs)
-    const firstStruct = structs[startNewStructs]
-    // write first struct with an offset (may be 0)
-    firstStruct.write(encoder, clock - firstStruct.id.clock, 0)
-    for (let i = startNewStructs + 1; i < structs.length; i++) {
-      structs[i].write(encoder, 0, 0)
-    }
+    writeStructs(encoder, store.clients.get(client), client, clock)
  })
-  // fill out diff to pos of end of message
-  encoding.setUint32(encoder, startMessagePos, encoding.length(encoder) - startMessagePos)
 }

 /**
 * @param {decoding.Decoder} decoder The decoder object to read data from.
- * @param {Map<number,number>} localState
- * @return {Map<number,IterableIterator<AbstractRef>>}
+ * @return {Map<number,Array<AbstractRef>>}
 */
-const readStructReaders = (decoder, localState) => {
+export const readClientsStructRefs = decoder => {
  /**
-   * @type {Map<number,IterableIterator<AbstractRef>>}
+   * @type {Map<number,Array<AbstractRef>>}
   */
-  const structReaders = new Map()
-  const endOfMessagePos = decoder.pos + decoding.readUint32(decoder)
-  const clientbeforeState = decoding.readVarUint(decoder)
-  for (let i = 0; i < clientbeforeState; i++) {
+  const clientRefs = new Map()
+  const numOfStateUpdates = decoding.readVarUint(decoder)
+  for (let i = 0; i < numOfStateUpdates; i++) {
+    const numberOfStructs = decoding.readVarUint(decoder)
    const nextID = readID(decoder)
-    const decoderPos = decoder.pos + decoding.readUint32(decoder)
-    const structReaderDecoder = decoding.clone(decoder, decoderPos)
-    const numberOfStructs = decoding.readVarUint(structReaderDecoder)
-    structReaders.set(nextID.client, createStructReaderIterator(structReaderDecoder, numberOfStructs, nextID, localState.get(nextID.client) || 0))
+    const refs = readStructRefs(decoder, numberOfStructs, nextID)
+    clientRefs.set(nextID.client, refs)
  }
-  // Decoder is still stuck at creating struct readers.
-  // Jump ahead to end of message so that reading can continue.
-  // We will use the created struct readers for the remaining part of this workflow.
-  decoder.pos = endOfMessagePos
-  return structReaders
+  return clientRefs
 }

 /**
@@ -175,86 +147,69 @@ const readStructReaders = (decoder, localState) => {
 *
 * @param {Transaction} transaction
 * @param {StructStore} store
- * @param {Map<number,number>} localState
- * @param {Map<number,IterableIterator<AbstractRef>>} structReaders
- * @param {Array<AbstractRef>} stack Stack of pending structs waiting for struct dependencies.
- *                                   Maximum length of stack is structReaders.size.
- * @param {IterableIterator<IterableIterator<AbstractRef>>} structReaderIterator
- * @param {IteratorResult<IterableIterator<AbstractRef>>} structReaderIteratorResult
 *
 * @todo reimplement without iterators - read everything in arrays instead
 */
-const execStructReaders = (transaction, store, localState, structReaders, stack, structReaderIterator, structReaderIteratorResult) => {
+const resumeStructIntegration = (transaction, store) => {
+  const stack = store.pendingStack
+  const clientsStructRefs = store.pendingClientsStructRefs
  // iterate over all struct readers until we are done
-  while (stack.length !== 0 || !structReaderIteratorResult.done) {
+  while (stack.length !== 0 || clientsStructRefs.size !== 0) {
    if (stack.length === 0) {
-      // stack is empty. We know that there there are more structReaders to be processed
-      const nextStructRes = structReaderIteratorResult.value.next()
-      if (nextStructRes.done) {
-        // current structReaderIteratorResult is empty, use next one
-        structReaderIteratorResult = structReaderIterator.next()
-      } else {
-        stack.push(nextStructRes.value)
-      }
-    } else {
-      const ref = stack[stack.length - 1]
-      const m = ref._missing
-      while (m.length > 0) {
-        const missing = m[m.length - 1]
-        if (!exists(store, missing)) {
-          // get the struct reader that has the missing struct
-          const reader = structReaders.get(missing.client)
-          const nextRef = reader === undefined ? undefined : reader.next().value
-          if (nextRef === undefined) {
-            // This update message causally depends on another update message.
-            // Store current stack and readers in StructStore and resume the computation at another time
-            store.pendingStructReaders.add({ stack, structReaders, missing, structReaderIterator, structReaderIteratorResult })
-            return
-          }
-          stack.push(nextRef)
-          break
-        }
-        ref._missing.pop()
-      }
-      if (m.length === 0) {
-        const localClock = (localState.get(ref.id.client) || 0)
-        const offset = ref.id.clock < localClock ? localClock - ref.id.clock : 0
-        if (offset < ref.length) {
-          if (ref.id.clock + offset !== localClock) {
-            // A previous message from this client is missing
-            // Store current stack and readers in StructStore and resume the computation at another time
-            store.pendingStructReaders.add({ stack, structReaders, missing: createID(ref.id.client, localClock), structReaderIterator, structReaderIteratorResult })
-            return
-          }
-          ref.toStruct(transaction.y, store, offset).integrate(transaction)
-        }
-        stack.pop()
+      // take any first struct from clientsStructRefs and put it on the stack
+      const [client, structRefs] = clientsStructRefs.entries().next().value
+      stack.push(structRefs.refs[structRefs.i++])
+      if (structRefs.refs.length === structRefs.i) {
+        clientsStructRefs.delete(client)
      }
    }
-  }
-  if (stack.length > 0) {
-    store.pendingStructReaders.add({ stack, structReaders, missing: stack[stack.length - 1].id, structReaderIterator, structReaderIteratorResult })
-  }
-}
-
-/**
- * Try to resume pending struct readers in `store.pendingReaders` while `pendingReaders.nextMissing`
- * exists.
- *
- * @param {Transaction} transaction
- * @param {StructStore} store
- */
-const tryResumePendingStructReaders = (transaction, store) => {
-  let resume = true
-  const pendingReaders = store.pendingStructReaders
-  while (resume) {
-    resume = false
-    for (const pendingReader of pendingReaders) {
-      if (exists(store, pendingReader.missing)) {
-        resume = true // found at least one more reader to execute
-        pendingReaders.delete(pendingReader)
-        execStructReaders(transaction, store, getStates(store), pendingReader.structReaders, pendingReader.stack, pendingReader.structReaderIterator, pendingReader.structReaderIteratorResult)
+    const ref = stack[stack.length - 1]
+    const m = ref._missing
+    const client = ref.id.client
+    const localClock = getState(store, client)
+    const offset = ref.id.clock < localClock ? localClock - ref.id.clock : 0
+    if (ref.id.clock + offset !== localClock) {
+      // A previous message from this client is missing
+      // check if there is a pending structRef with a smaller clock and switch them
+      const structRefs = clientsStructRefs.get(client)
+      if (structRefs !== undefined) {
+        const r = structRefs.refs[structRefs.i]
+        if (r.id.clock < ref.id.clock) {
+          // put ref with smaller clock on stack instead and continue
+          structRefs.refs[structRefs.i] = ref
+          stack[stack.length - 1] = r
+          // sort the set because this approach might bring the list out of order
+          structRefs.refs = structRefs.refs.slice(structRefs.i).sort((r1, r2) => r1.id.client - r2.id.client)
+          structRefs.i = 0
+          continue
+        }
      }
+      // wait until missing struct is available
+      return
+    }
+    while (m.length > 0) {
+      const missing = m[m.length - 1]
+      if (!exists(store, missing)) {
+        const client = missing.client
+        // get the struct reader that has the missing struct
+        const structRefs = clientsStructRefs.get(client)
+        if (structRefs === undefined) {
+          // This update message causally depends on another update message.
+          return
+        }
+        stack.push(structRefs.refs[structRefs.i++])
+        if (structRefs.i === structRefs.refs.length) {
+          clientsStructRefs.delete(client)
+        }
+        break
+      }
+      ref._missing.pop()
+    }
+    if (m.length === 0) {
+      if (offset < ref.length) {
+        ref.toStruct(transaction.y, store, offset).integrate(transaction)
+      }
+      stack.pop()
    }
  }
 }
@@ -271,6 +226,43 @@ export const tryResumePendingDeleteReaders = (transaction, store) => {
  }
 }

+/**
+ * @param {Map<number,{refs:Array<AbstractRef>,i:number}>} pendingClientsStructRefs
+ * @param {number} client
+ * @param {Array<AbstractRef>} refs
+ */
+const setPendingClientsStructRefs = (pendingClientsStructRefs, client, refs) => {
+  pendingClientsStructRefs.set(client, { refs, i: 0 })
+}
+
+/**
+ * @param {encoding.Encoder} encoder
+ * @param {Transaction} transaction
+ */
+export const writeStructsFromTransaction = (encoder, transaction) => writeClientsStructs(encoder, transaction.y.store, transaction.beforeState)
+
+/**
+ * @param {StructStore} store
+ * @param {Map<number, Array<AbstractRef>>} clientsStructsRefs
+ */
+const mergeReadStructsIntoPendingReads = (store, clientsStructsRefs) => {
+  const pendingClientsStructRefs = store.pendingClientsStructRefs
+  for (const [client, structRefs] of clientsStructsRefs) {
+    const pendingStructRefs = pendingClientsStructRefs.get(client)
+    if (pendingStructRefs === undefined) {
+      setPendingClientsStructRefs(pendingClientsStructRefs, client, structRefs)
+    } else {
+      // merge into existing structRefs
+      const merged = pendingStructRefs.i > 0 ? pendingStructRefs.refs.slice(pendingStructRefs.i) : pendingStructRefs.refs
+      for (let i = 0; i < structRefs.length; i++) {
+        merged.push(structRefs[i])
+      }
+      pendingStructRefs.i = 0
+      pendingStructRefs.refs = merged.sort((r1, r2) => r1.id.clock - r2.id.clock)
+    }
+  }
+}
+
 /**
 * Read the next Item in a Decoder and fill this Item with the read data.
 *
@@ -283,11 +275,9 @@ export const tryResumePendingDeleteReaders = (transaction, store) => {
 * @private
 */
 export const readStructs = (decoder, transaction, store) => {
-  const localState = getStates(store)
-  const readers = readStructReaders(decoder, localState)
-  const structReaderIterator = readers.values()
-  execStructReaders(transaction, store, localState, readers, [], structReaderIterator, structReaderIterator.next())
-  tryResumePendingStructReaders(transaction, store)
+  const clientsStructRefs = readClientsStructRefs(decoder)
+  mergeReadStructsIntoPendingReads(store, clientsStructRefs)
+  resumeStructIntegration(transaction, store)
  tryResumePendingDeleteReaders(transaction, store)
 }

@@ -307,6 +297,6 @@ export const readModel = (decoder, transaction, store) => {
 * @param {Map<number,number>} [targetState] The state of the target that receives the update. Leave empty to write all known structs
 */
 export const writeModel = (encoder, store, targetState = new Map()) => {
-  writeStructs(encoder, store, targetState)
+  writeClientsStructs(encoder, store, targetState)
  writeDeleteSet(encoder, createDeleteSetFromStructStore(store))
 }